To make the caramelized onions:
Melt the butter and olive oil in a large sauté pan over medium-low heat. Add onions and stir to coat. Cook for 20 minutes, stirring occasionally. Sprinkle the salt and sugar over the onions and continue to cook for another 30 -45 minutes, stirring occasionally. You’re looking for a deep, rich brown color. They may start to stick to the pan a little. It’s OK if they form a bit of a crust, but don’t let them burn. Two minutes before removing the onions from the heat, add the garlic and crushed red pepper flakes and sauté. Remove from heat and set aside to cool.
To make the pizza:
Preheat the oven to 425°F. Lightly grease a sheet pan. Set aside.
Roll dough into a rectangle slightly larger than the sheet pan. Place dough on pan, prick with fork in several places and bake for 8 minutes.
Remove pan from oven and lightly brush top of crust with olive oil. Layer on half of the Dubliner cheese followed by the onions, bacon and spinach. Top with remaining Dubliner and Parmesan cheese.
Bake for another 12-14 minutes or to desired degree of doneness. Remove from oven and allow to cool for 5 minutes before slicing and serving.